Word has no facility for highlighting parts of speech. For prepositions, though, you could use Find/Replace to highlight them all, then remove the highlights when you're done editing. A macro you could use to expedite this is:
Code:
Sub Demo()
Application.ScreenUpdating = False
Options.DefaultHighlightColorIndex = wdYellow
Dim StrFnd As String, i As Long
StrFnd = Array("above", "about", "across", "against", "along", _
"among", "around", "at", "before", "behind", "below", "beneath", _
"beside", "between", "beyond", "by", "down", "during", "except", _
"for", "from", "in", "inside", "into", "like", "near", "of", _
"off", "on", "since", "to", "toward", "through", "under", _
"until", "up", "upon", "with", "within")
With ActiveDocument.Range.Find
.ClearFormatting
.Replacement.ClearFormatting
.Forward = True
.Wrap = wdFindContinue
.MatchCase = True
.MatchWholeWord = True
.MatchWildcards = False
.MatchSoundsLike = False
.MatchAllWordForms = False
.Replacement.Text = "^&"
.Replacement.Highlight = True
For i = 0 To UBound(StrFnd)
.Text = StrFnd(i)
.Execute Replace:=wdReplaceAll
Next
End With
Application.ScreenUpdating = True
End Sub
When you're done editing, you can re-run the macro with:
.Replacement.Highlight = False
instead of:
.Replacement.Highlight = True
For PC macro installation & usage instructions, see:
http://www.gmayor.com/installing_macro.htm
For Mac macro installation & usage instructions, see:
http://word.mvps.org/Mac/InstallMacro.html